Combined inductance and capacity tuner



Sept. 27, 1949. J. RENNICK 2,483,105

COMBINED INDUCTANCE AND CAPACITY TUNER Filed Oct. 3, 1945 HIS ATTORNEYSPatented Sept. 27, 1949 COMBINED INDUCTANUE AND CAPACITY TUNER John L.Renniok, Elmwood Park,

Zenith Radio Corporation,

Illinois 111., asslgnor a corporation of Application October 3, 1945,Serial No. 020,088

The present invention relates to tuners for radio apparatus particularlyof the type which are arranged to receive or transmit energy indifferent frequency bands.

It is desirable in commercial radio apparatus arranged to transmit orreceive energy in a plu- 4 rality of allocated bands in the frequencyspectrum useful for radio apparatus to be able to tune such apparatuseasily, with the least number of inexpensive parts arranged compactly.

It is an object of the present invention to provide improved apparatusfor obtaining the above mentioned desiderata and yet position the tuningelements where they cause the least electrical interference, coupling,etc., to the other elements in the composite apparatus.

Another object of the present invention is to provide improved apparatuswherein an inductance or condensermay be varied or adjusted by actuationof a common control element.

A further object of the present invention is to provide an improvedconstruction for tuners useful in radio apparatus tunable to differentfrequency bands.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention itself, both as to itsorganization and manner of operation,together with further ob- Jects and advantages thereof, may best beunderstood by reference to the followingdescription taken in connectionwith the accompanying drawing in which:

Figure 1 is a perspective view, partly in section, of apparatusincorporating the present invention, and

Figs. 2 and 3 are views, partly in section, showing some of the detailsof the apparatus of Fig. 1.

The tuning arrangement described isespecially applicable in radioreceivers arranged to receive amplitude modulated signals in thestandard broadcast band ranging from 550 to 1600 kilocycles and also toreceive frequency modulated signals in the broadcast band assignedthereto. The arrangement is such that a condenser I of the rotary typeis varied for receiving amplitude modulated signals and an inductance 2of the variable core type is varied for receiving frequency modulatedsignals, the condenser and inductance each being varied by actuation ofa single common control shaft 3.

The condenser I is shown of the rotary interleaved type of which the oneset of spaced leaves rotatably mounted are each arranged to besandwiched in varying degrees between adjacent 2 leaves one secondrelatively stationary set oi spaced leaves as the control shaft 3 isrotated between its extreme limits of movement.

The condenser I is mounted resiliently on the chassis 4, rubber or othersimilar elastic material I being interposed between the chassis 4 andcondenser supports 8 each of which has one end thereof fixed to thestationary frame portions of condenser I and the other end thereofresiliently mounted in the doughnut-shaped resilient material 5.

Control shaft 3 fixed to the rotatably mounted plates of condenser I haspermanently mounted thereon by means of set screw 1 cam member I havinga hub 9 fixed to shaft 3. The angular position of cam 8 is related tothe magnitude of inductance unit 2 as will appear from the followingdescription;

Inductance unit 2, comprising stationary coil III wound on coil form IIand movable core member I2, is mounted on the stationary portion ofcondenser I by means of bracket I3, one end of bracket I3 being fixed tothe stationary portion of condenser 'I by means of a suitable fastenerI4 and the other end of the bracket being fixed to coil form II. Coremember I! is fastened to a flexible actuating member I 5 which has athreadlike outer surface arranged to be held in adjusted position in acooperating threaded insulating member I8 forming a part of a carriageII. The flexible actuating member I5 is made preferably as set forth andclaimedin the Patent Number 2,423,275, July 1, 1947, to Clarence W.Wandrey,

and assigned to the same assignee as the present application.

Obviously the actuating member I 5 must not be flexible in the directionof its length because the tuning core members I2 must be moved in unisonwith each other accurately to maintain accurate tuning. That is, themembers It must be inextensible and incompressible within the range offorces which they encounter in the tuner. The term "inextensible is usedto mean that members I 5 must not increase or decrease their lengthwithin the range of forces which they encounter in the tuner, yet, atthe same time, they must be flexible laterally to allow sidewardbending. This lateral flexibility of members I5 makes it possiblefor'the tuning cores I2 to slide in accurately defined passages throughthe coil forms II when moved by the carriage I1 even though the portionI6 of carriage I'l moves through the arc of a circle. By thisarrangement, linkages with their inevitably associated play and backlashor complicated arrangements for essence 3 eliminating play and backlashare entirely avoided.

The carriage it, the angular position of which determines the positionof core members 12 and hence the magnitude of the inductance unit 2, ispivotally mounted on the stationary frame portion of the condenser unitI. These pivots i8 and i9 consist of antifriction balls and 21,respectively, being set into their respective seats. These seats for theballs 20 and 2| are formed by drilling or punching undersized holes,on'the same longitudinal axis, through a carriage flange 22, a pair ofstationary frame portions 22, 24 of condenser unit I and a flexibleextension of carriage 11. Ball 20 is held in its seats between members22 and 23, and ball 2| is held in its seats between members 24 and 25due to the resilient nature of the spring 25 thus providing the pair ofantifriction pivot points l8, IS on the stationary portions 23, 24 ofcondenser 1 upon which the carriage I1 is pivoted.

A tension spring 26, having one of its ends fastened to the carriage Hat a point 21 and its other end fastened to an extension 28 of thestationary frame portion of the condenser I,

biases the carriage ll counterclockwise about the pivot points l8, l9and holds a flat surface 29, forming a part of carriage II, in positiveengagement with cam member 8. Not only the inherent friction between therotating parts of the condenser and the frame of the condenser, but alsothe friction between the cam edge and the surface 29 is suilicient tokeep the cm from moving until the cam is rotated by the control shaft 2.

In Figure -3, upon counterclockwise rotation of the cam 8, the flatsurface 29 rides smoothly without binding on the cam because the surfaceof the cam approaching the flat surface 29 is of ever decreasing radius.

Upon counterclockwise rotation of the control shaft 3, the cam 2 isrotated counterclockwise and by reason of the biasing spring 20 biasingthe flat surface 29 against the cam 8 and also because the pivotalposition of the carriage i1 is determined by the radius of that portionof the cam against which it bears, the carriage is pivoted more and morecounterclockwise as that portion of the cam against which it bearsreduces its radius. As the carriage i1 is pivoting counterclockwise onpivots l8, l9 by its interaction with the ever decreasing radius portionof the cm 8, its portion I0 is rising in an arc. As flexible actuatingmember I! is a non-extensible connection between portion I2 and themovable core member 12, the rising motion of portion 19 is transmittedwithout backlash to the core member, to raise the core member and changethe tuning of the inductance 2.

Conversely, clockwise rotation of the cam I results in pivoting thecarriage clockwise, to lower the core member and change the tuning ofthe inductance 2.

Control shaft 3 is arranged to be rotated by rotating manual controlknob 30, shaft 2| of knob 30 being connected to shaft 2 through belt 22and pulley 23. The shaft 2| may be connected to station indicatingapparatus for indicating the tuned condition of condenser l andinductance 2. One of the features of the present invention is that thetuning inductance unit 2 may be mounted underneath the chassis l inclose proximity to the terminals of tube sockets of conventionalconstruction and yet be resiliently mounted with respect to the chassisl by providing a clearance opening be between the chassis d and coilform Another feature is that the chassis 4, since it has condenser unitl mouhted on the one side thereof and the inductance unit 2 mounted onthe other side thereof, serves as an electrostatic shield for shieldingsuch units one from the other.

This combination condenser and inductance tuning unit has particularadvantages in that only a single tuning knob is effective for tuning anydesired signal in the broadcast band. This tuning is accomplished byadjustment of the condenser connected in conventional manner throughconventional band switch with the oscillator and radio frequencycircuits in a superheterodyne receiver. Alternatively, in a secondposition of such conventional band switch the unit is tuned with thesame knob to any desired signal in the frequency modulation band byadjustment of the inductance coils connected in conventional mannerthrough terminals 21, 28 and such switch with the oscillator and radiofrequency circuits in the receiver.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects, and, therefore, the aim in theappended claim is to cover all such changes and, modifications as fallwithin the true spirit and scope of this invention.

I claim:

A tuning device including a frame member, a shaft member rotatablymounted on said frame member, a cam member fixedly mounted on said shaftmember, a carriage member pivotally mounted on said frame along an axisof said carriage and having portions extending on either side of saidaxis, a further member formed on one of said portions and adapted tocoast with the edge of said cam, an inductance coil having alongitudinally movable core member mounted therein, a longitudinallyinextensible and laterally flexible connecting element coupling saidcore to the other of said portions, spring means for biasing saidcarriage about said axis in a direction to urge said further memberagainst the edge of said cam and to cause said last mentioned portion todescribe an are moving said core longitudinally in said inductance to acertain position by means of said connecting element, whereby rotationof said shaft causes said last mentioned portion to describe furthersaid are and said core to move in substantially a straight line withinsaid inductance.

JOHN L. RENNICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Name Date 1,659,417 Washington Feb. 14, 1928 2,206,820 MydlllJuly 2, 1940 2,217,984 Kirk Oct. 15, 1940 2,270,117 Fill Jan. 13, 19422,320,483 Stocker June 1, 1943 FOREIGN PATENTS Number Country Date112,516 Australia Feb. 7, 1941

